Received: 5 September 2020
Accepted: 22 September 2020
First Online: 12 October 2020
Ethics approval and consent to participate
: All procedures performed in studies involving human participants were in accordance with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. We signed the ‘Surveillance, Epidemiology, and End Results Program Data Use Agreement’ in accordance with the requirement of using SEER database. Approval was waived by the local ethics committee, as SEER data is publicly available and de-identified.
: All authors listed approved the publication of the manuscript<b>.</b>
: All authors declare that they have no conflicts of interest.